Bonsai Leaves Sticky

I came to this party late, but definitely the flat foreign bodies are scale insects and they secrete the sticky exudate. For future reference, you really don't have to spray the whole tree. Just soak a Q-tip in rubbing alcohol and touch it to each one. Gets rid of them promptly. The only thing is, since they are hard to spot, you really do have to go over the whole tree including under sides of the leaves very carefully to make sure you got them all.

The ants don't eat the insects, they eat the honeydew, the sticky exudate. Aphids produce it too, so ants have been known to "farm" aphids to keep a source of honeydew handy. Get rid of the scale insects/ ants and wash the honeydew off and the ants will go away. It's good to get the honeydew off, because it also makes a welcoming environment for a black mold.